The following will deal, by way of example only, with the detection of a gas in a fluid which is a dielectric fluid.
Electrical systems are well known in the art which use a dielectric fluid as an insulating substance; these systems include for example transformers, circuit breakers and the like.
It is known that, in the event of a disturbance or malfunction of an above mentioned type of device or system, the result may be the production of one or more undesired gases in the insulating fluid; this may occur for example if a device is working at high temperature or high conditions of electrical stress therein. Such conditions may also produce undesired moisture and/or one or more breakdown products of the dielectric material of the insulating system (i.e. insulating fluid). If such abnormal conditions are allowed to continue uncorrected, this may lead to irreparable damage to the electrical system. A timely (e.g. more or less immediate) detection and/or diagnosis of any such abnormal operation of an electrical apparatus is thus advantageous in order to be able to avoid irreparable harm to such a system.
Accordingly, various monitoring devices and systems have been proposed for the detection of any incipient failure conditions such as for example any undesired increase of the concentration of a fault gas (e.g. a combustible gas such as for example, hydrogen gas, carbon monoxide gas, methane gas, ethane gas, ethylene gas, acetylene gas and the like or a non-combustible gas such as for example, carbon dioxide), moisture (e.g. water), a breakdown product, contaminant substance, and/or the like contained (e.g. dissolved) in the insulating fluid.
Some such detection and/or monitoring systems are, for example, described in Canadian Patent no. 1,054,223 (Belanger), U.S. Pat. No. 4,112,737 (Morgan), U.S. Pat. No. 4,293,399 (Belanger et al), U.S. Pat. No. 4,271,474 (Belanger et al), U.S. Pat. No. 5,070,738 (Morgan) and U.S. Pat. No. 5,271,263 (Gibeault). The entire contents of these patent references as well as any other patent or other types of references which are mentioned therein are incorporated herein by reference.
For example, U.S. Pat. No. 4,293,399 describes how the concentration of gaseous hydrogen dissolved in a fluid may be determined by a measure of an electric current generated by electro-chemical oxidation of the gaseous hydrogen at an electrode of the detector. The prior art detecting and measuring means described in this U.S. patent comprises a polymeric membrane permeable to hydrogen gas for contact with a fluid containing dissolved hydrogen gas; an electrolyte capable of facilitating oxidation of the hydrogen gas diffused through the polymeric membrane at a first electrode and reduction of an oxygen-containing gas such as air at a second electrode; and a measuring device connected across the electrode for measuring the intensity of the electrical current generated by the electrochemical reaction of oxidation of the hydrogen gas, this intensity being proportional to the concentration of hydrogen in the fluid.
It is advantageous for such monitoring (e.g. detection) devices, as described above, to be able to provide an accurate as possible detection and/or diagnosis of the incorrect operation of systems such as, for example, transformers, circuit breakers, shunt reactors or any electro-apparatuses using a dielectric fluid as an insulating substance such as a dielectric liquid (e.g. a dielectric oil) or a dielectric gas (e.g. SF.sub.6 gas).
A number of the above mentioned prior art monitoring devices or systems have the drawback that the sample gas received by the detector may have a relatively low concentration of a target gas which it is desired to detect or monitor; e.g. a low concentration of acetylene gas relative to hydrogen gas. In such case, the low concentration of a target gas relative to the other gases present in a sample gas may be such that one or more of the other gases may interfere with the measurement of a predetermined target gas(es). In other words, the precision of the results of the detecting or monitoring device may thus be less than is desired; i.e. due to that fact that one or more extraneous gases may interfere with the reading of the target gas.
Accordingly, it would be advantageous to be able to facilitate analysis (e.g. detection) of one or more predetermined individual gases (i.e. target gases) of a sample gas mixture. It would, in general, be advantageous to be able obtain a sample gas enriched in a target gas, the presence of which is to be the subject of an analysis and/or separate from a sample gas mixture at least one target gas which is to be subjected to analysis. It would, further be advantageous to be able to facilitate analysis of target gases of a sample gas by separating one or more such target gases from the sample gas, the so separated target gas then being subjected to detection.